What I really find ironic is some people will obscure their license plate, but then provide a VIN (presumably for Carfax purposes). I have no issue with displaying the plate, and really don't have an issue with providing a VIN. However, I have seen car thieves use other vehicle's VINs to make a fake VIN plate so that it returns as a valid VIN. Even still, I would provide my VIN to a prospective buyer unless I had a bad feeling about them. I have no idea what somebody could use your license plate for.
But much like license plates, your VIN is almost as visible when parked.